Hannah Anderson, James Lee DiMaggio search focuses on Idaho wilderness

Updated 8:20 PM ET

CASCADE, Idaho Federal and local law enforcement agents say they're focused on getting feet on the ground in the search for 16-year-old Hannah Anderson and her suspected abductor, 40-year-old James Lee DiMaggio in central Idaho's Frank Church River of No Return Wilderness.

Helicopters and fixed-wing aircraft have been flying FBI agents and other law enforcement officers into the roadless wilderness area throughout the day Saturday.

"We are going to continue searching for as long as we believe this is the area most likely where this pair would be," Ada County Sheriff's spokeswoman Andrea Dearden said. "We're going to put every resource possible here, every person possible that we can."

As CBS affiliate KMVT Twin Falls reported Saturday, officials don't have a nighttime plan. Dearden said it appeared operations will be halted overnight and that the search will resume on Sunday.

Detectives with the San Diego County Sheriff's Department finished searching DiMaggio's car Saturday afternoon at the remote trailhead where it was found about 40 miles east of the tiny town of Cascade. They had the vehicle towed to a garage in Cascade for further processing.

DiMaggio is suspected of killing Hannah's mother Christina Anderson, 44, and her 8-year-old brother Ethan Anderson, whose bodies were found Sunday night in DiMaggio's burning house in California near the Mexico border.

Ethan Anderson's remains were not positively identified until Friday night, when the San Diego County Sheriff's Department said its crime lab had used DNA to determine Ethan's identity. An Amber Alert was initially issued for both children.

The steep and mountainous terrain makes it impossible to do a traditional grid search — and the search area itself spans more than 300 miles, Dearden said. Though search dogs have been brought in from out of state and horses have been identified for possible use, the animals aren't currently helping in the search, Ada County Sheriff's spokeswoman Andrea Dearden said Saturday afternoon.

Time is a critical concern. Dearden said investigators believe both Hannah and DiMaggio are alive, but they are worried about whether the 16-year-old has the right clothing and footwear for the mountainous conditions and whether she has the stamina to handle days of hiking through steep terrain.

Instead, search coordinators are trying to choose the most strategic locations to place the searchers, whether it be along trailheads, at the few airstrips within the wilderness borders, or along drainage paths and river shores.

It's Idaho's wildfire season, and though no blazes threaten the search area, smoke from big fires to the south has reduced visibility and ash is falling on the town of Cascade.

Though Dearden said the smoke hasn't yet hindered the search, nightfall is a problem.

"Simply for safety reasons it isn't practical to have people out there at night," she said.

Ray Arnold, a backcountry pilot and the owner of charter flight service Arnold Aviation in Cascade, said he flew local crews into the wilderness area to help with the search on Friday.

On Saturday, he was helping law enforcement out at the Cascade Airport, fueling aircraft and offering other support, he said.

"There's quite a bit of smoke but you know, if you get down a little lower, it's fine. It's not anything different than any other summer around here," Arnold said.

Though there's not a ton of tree canopy cover in the high alpine area where Anderson and DiMaggio are believed to be, it would still likely be difficult to spot the pair from a plane, Arnold said.

"If a person stands beside a tree or something and his clothes are similar to surroundings, it's hard to see a person, especially if they're not moving," Arnold said. "The people on the ground are probably using spotting scopes and they have a better chance of finding them in some ways. A person gets pretty small when you're up in the air."

Law enforcement officials in San Diego have noted that DiMaggio bought camping gear a few weeks ago.